Pressure headbox for web forming machine



Sept. 12, 1967 v. s. GRATER 3,341,400

PRESSURE HEADBOX FOR WEB FORMING MACHINE Filed Dec. 21, 1964 6SheetsSheet 1 INVENTOR V. S. GRATER V. S. GRATER Sept. 12, 1967 PRESSUREHEADBOX FOR WEB FORMING MACHINE 6 Sheets-Sheet 2 Filed Dec 21, 1964INVENTOR V. S. GRATER Sept. 12, 1967 v. s. GRATER PRESSURE HEADBOX FORWEB FORMING MACHINE 6 Sheets-Sheet 3 Filed Dec. 21, 1964 III III

INVENTOR V. S. GRATER Sept. 12, 1967 v. s. GRATER 3,341,400

PRESSURE HEADBOX FOR WEB FORMING MACHINE Filed Dec. 21, 1964 6Sheets-Sheet 4 Plzsssuee 256.

INVENTOR V. S. GRATER V. S. GRATER Sept. 12, 1967 PRESSURE HEADBOX FORWEB FORMING MACHINE 6 Sheets-Sheet Filed Dec. 21, 1964 lNVE/VTOR V. S.GRATER FIG. 9

Sept 1967 v. s. GRATER 3,341,400

PRESSURE HEADBOX FOR WEB FORMING MACHINE Filed Dec. 21, 1964 6Sheets-Sheet 6 FIG. 10

INVENTOR V. S. GRATER United States Patent ABSTRACT OF THE DISCLOSUREThe structure of a paper machine headbox includes an encompassingreaction frame to contain working forces, particularly the pressure ofstock acting against the movable portion of the headbox slice, the forcetransmitting members including hydraulic connecting members pressurizedin response to the pressure of stock in the headbox.

This invention relates to an improved headbox of the type used to supplypaper stock to a paper making machine web forming section whoseconfiguration limits the space available for the positioning of theheadbox, or whose configuration necessitates unconventional positioningof the 'headbox. Such web forming sections are shown and described inUS. Patents Nos. 2,882,966, 2,995,186 and 3,056,719.

An essential requirement in the manufacture of paper is that paper stockis deposited from the headbox onto the web forming section in a streamof constant thickness across the width of the machine. Thus, anessential requirement of headbox design is that the slice lips, throughwhich the stock flows, maintain a gap substantially parallel across theWidth of the machine, under all operating conditions.

The pressure of the paper stock in the headbox, necessary to provide therequired stock discharge velocity, acts on the structural members of theheadboX which are conventionally the lower slice lip and apron memberand the upper slice lip and roof member. When the slice lips apart andcauses the gap to increase to a maximum dimension in the centralunsupported portion of the slice lips and thus discharge a stream ofpaper stock of uneven thickness.

In conventional paper machine headboxes, where space limitations are notthe major consideration, it is a simple matter to reinforce the slicelip supporting structure, and to provide pressure compensating means,such that the gap between the slice lips is maintained constant acrossthe width of the machine.

However, in paper machines of the type shown and described in US.Patents Nos. 2,882,966, 2,995,186 and 3,056,719, it is necessary thatthe headboxes be positioned to eject a stream of stock in asubstantially downward direction and also that the headboxes berepositioned to suit varying operating conditions, where it is necessaryto eject a stream of stock onto the web forming section at differentangles. Under these conditions it is not possible to provide slice lipreinforcing and pressure compensating means similar to those used onconventional stationary headboxes.

The present invention overcomes this and other disadvantages byproviding a headbox which is adjustably suspended from an overheadsupport structure to permit a stream of stock to be ejected downwardly,at different angles, onto a forming section, and in which deflection ofthe roof and apron members of the headbox, which support the slice lips,are minimized by the provision of a rectangular support frame, the planeof which is substantially normal to the direction of stock flow throughthe headbox, and which surrounds the apron and roof members, and isadjustable therewith. The apron member is pivotally connected in themachine width direction, at approximately quarter point positions, toone side of the rectangular support frame. The adjustable roof member isconnected in the machine width direction, at approximately quater pointpositions, to the opposing side of the rectangular support frame bymeans of flexible pressure cells, such as hydraulic cylinders, to permitdeflection minimizing reaction forces to be applied to the roof memberin all positions of adjustment. When hydraulic cylinders are used, thepressure in the cylinders is controlled by a hydraulic circuit, inresponse to pressure sensing means positioned in the roof member andflush with the surface of the stock flow passage through the headboX, toprovide increased or decreased reaction forces in accordance withincreased or decreased pressures of stock flow through the headbox.

It is, therefore, the main object of this invention to provide a headboxwhich is adjustably supported from an overhead structure to eject astream of stock substantially downwardly and which embodies means toapply reaction forces to minimize deflections in the apron and roofmembers, in all positions of headbox adjustment and all slice openings.

Another object of this invention is to provide a headbox in which themeans to apply reaction forces includes a reaction frame surrounding thehead box and in which substantially all deflections, due to the reactionforces, are absorbed by the reaction frame.

Another object of this invention is to provide a headbox, as outlined inthe main objective above, in which the apron and roof member reactionforces are automatically adjusted to compensate for changes in thepressure of the stock flowing through the headbox.

Another object of this invention is to provide a headbox, as outlined inthe main objective above, which incorporates a flexible plate type hingeto provide adjustment of the gap between the slice lips and to providean obstruction free passage for the flow of stock through the headbox.

A further object of this invention is to provide a head boxincorporating a flexible plate type hinge and includ ing a linkagemechanism positioned at each side of the headbox to provide formechanical adjustment of the gap between the slice lips and to preventany loads be ing imposed on the flexible plate hinge.

These and other objects and advantages of this invention will be furtherapparent by referring to the following detailed specification andfigures, in which:

FIG. 1 is a side view of a headbox and supporting structure embodyingthe features of this invention.

FIG. 2 is a plan view of the headbox and supporting structure shown inFIG. 1.

FIG. 3 is a sectional view on 3-3 in FIG. 1.

FIG. 4 is a sectional view on 4-4 in FIG. 2.

FIG. 5 is an enlarged view of the hinge details shown encircled at 5 inFIG. 4.

FIG. 6 is an enlarged side View of the headbox and linkage mechanismshown in FIG. 1.

FIG. 7 is a sectional view on 7-7 in FIG. 6.

FIG. 8 is a sectional view on 8-8 in FIG. 6.

FIG. 9 is a sectional view on 9-9 in FIG. 6.

FIG. 10 is a schematic representation of the linkage mechanism.

FIG. 11 is a schematic representation of the linkage mechanism adjustedto provide a relatively narrow gap between the headbox slice lips.

FIG. 12 is a schematic representation of the linkage mechanism adjustedto provide a relatively wide gap between the headbox slice lips.

FIG. 13 (appearing on the same sheet as FIGS. 4 and- 5) is a hydrauliccircuit diagram of the stock pressure sensing and roof member deflectioncompensating arrangement.

Referring particularly to FIGS. 14, the headbox and reaction frameassembly, shown generally as 21, is pivotally suspended from an overheadsupport structure, shown generally as 22. Overhead support structure 22includes two support columns 23 positioned on each side of the machine,an overhead tie beam 24 connecting the upper ends of support columns 23on each side of the machine, and an overhead support beam 25 connectedto, and positioned between, each tie beam 24.

Headbox and reaction frame assembly 21 is pivotally suspended fromoverhead support structure 22 at approximately quarter point positionsto provide for minimum deflection. This is in accordance with the wellknown principle that the deflection of a uniformly loaded beam will be aminimum if the beam is simply supported at its quarter point positions,that is, the supports positioned a distance in from each end of the beamequal to one quarter the length of the beam.

The headbox and reaction frame assembly suspension mechanism compriseslifting jacks 26, position upon, and extending through support beam 25.Cross-shaft 27 extends between lifting jacks 26 to provide simultaneousoperation for lifting and lower ing of headbox and reaction frameassembly 21. Crossshaft 28 extends between one of the lifting jacks 26and a power source, such as hydraulic motor 29, positioned on one of thetie beams 24 and adapted to operate lifting jacks 26.

Headbox and reaction frame assembly 21 comprises two support frames 30,headbox assembly 31 and reaction frame assembly 32. Support frames arepivotally attached to lifting jacks 26 by pivot pins 33, and rigidlysupport headbox assembly 31, at the quarter point positions, by means ofapron support member 34, central support members and roof supportmembers 36. Reaction frame assembly 32 is slidably supported by apronsupport members 34 and reaction frame extension assemblies 37, which arerigidly attached to roof support members 36.

Headbox assembly 31 comprises three main portions, apron member 38, roofmember 39 and inlet member 40, with the adjacent surfaces of apronmember 38 and inlet member forming stock inlet passage 41, and theadjacent surfaces of roof member 39 and inlet member 40 forming stockinlet passage 42.

Cross-flow stock inlet 43 communicates with stock inlet passage 41 andis attached to the adjacent outer surfaces of apron member 38 and inletmember 40. Crossflow stock inlet 44 communicates with stock inletpassage 42 and is attached to the adjacent outer surfaces of roof member39 and inlet member 40. It will be understood that cross-flow stockinlets 43 and 44 are shown thus for illustration purposes only, and thatother stock inlet arrangements can be embodied in the headbox assemblywithout departing from the spirit of this invention.

Stock inlet passages 41 and 42 converge into a common stock passage 45,which is terminated by a stock discharge slot formed by the gap 46between apron slice lip 47 and roof slice lip 48. Stock passagebasically comprises stock accelerating portion 49 adjacent theconverging point of stock'inlet passages 41 and 42, a deceleratingportion 50 and a further accelerating portion 51 between slice lips 47and 48.

Apron member 38 forms one surface of stock passage 45 and includes apronslice lip 47. Apron member 38 is suspended from apron support members 34and is pivotally connected at the quarter point positions to apronreaction member 52, of reaction frame assembly 32, by means of pivotpins 53. Apron reaction member 52 is designed to provide a very highresistance to bending in the plane normal to the flow of stock throughthe headbox and thus provides the necessary reaction to the outwardloads imposed on apron member 38 by the pressure of the stock flowingthrough stock passage 45.

Roof member 39 embodies the means for adjustment of gap 46 between slicelips 47 and 48 and basically comprises fixed roof portion 54, andadjustable roof portion 55 which forms the other surface of stockpassage 45 and includes roof slice lip 48. This enables slice gap 46 tobe varied to suit stock and product requirements. Fixed and adjustableroof portions 54 and '55, respectively, are operatively connectedtogether by flexible plate type hinge 56. Reference to FIG. 5 shows thatflexible plate type hinge 56 provides a solid connection between fixedroof portion 54 and adjustable roof portion 55, thus ensuring noobstruction to the flow of stock through stock passage 45, whilst thereduced thickness portion 57 of hinge 56 provides the required hingeflexibility.

Fixed roof portion 54 is suspended from roof support members 36, andadjustable roof portion 55 is connected to roof reaction member 58 ofreaction frame assembly 32, at the quarter point positions, by means ofhydraulic cylinders 59, which are required to limit the deflection ofadjustable roof portion 55 and apron member 38 when acted upon by thehydraulic pressure of stock flowing through stock passage 45. Bylimiting this deflection the variation in gap 45, across the width ofthe machine, is kept to a minimum. The circuit diagram shown in FIG. 13(detailed later in this specification) allows this deflection to beresisted automatically in response to changes in hydraulic pressurewithin the headbox.

Roof reaction member 58 is designed to embody less resistance to bendingin the plane normal to the flow of stock through the headbox, than apronreaction member 52, and thus will deflect under highl oading fromhydraulic cylinders 59 and prevent high stresses being imposed upon theheadbox. The feature whereby reaction frame assembly 32 is supportedvertically but allowed to slide horizontally relative to headboxassembly 21, allows the headbox and reaction frame assembly 21 to assumea balanced state, when the loads are such that roof reaction member '58is caused to deflect.

Apron reaction :member 52 and roof reaction member 58 are connectedtogether to form a substantially rectangular reaction frame assembly byend members 60 and 61.

Apron reaction member 52 is arranged to be supported vertically by apronsupport members 34, and to be slidable relative thereto, by studs 62which are threaded at each end, one threaded end of each stud 62 beingsecurely screwed into apron support members 34, the other threaded endspassing through slots in apron reaction member 52 and, together withclamping plates 63 and nuts 64, slidably and securely supporting apronreaction member 52. Nuts 64 are adjusted to provide the requiredhorizontal slidability between apron support members 34 and apronreaction member 52, whilst also providing effective vertical support.

Roof reaction member 58 is arranged to be supported verticaly byreaction frame extension 37, and to be slidable relative thereto, bylower support brackets 65. Lower support brackets are adjustably boltedto reaction frame extension 37 by bolts 66, to provide verticaladjustment for the required horizontal slidability between roof reactionmember 58 and reaction frame extension 37, whilst also providingeffective vertical support.

Apron member 38, roof member 39 and inlet member 40, are joined to formthe complete headbox by conventional means, such as bolting.

End covers 67 and 68 are securely and rigidly bolted to the end platesof apron member 38, inlet member 40 and fixed roof portion 54, andprovide end closures for stgck inlet passages 41 and 42 and common stockpassage Reference to FIG. 9 shows a detail of a seal member (on one sideof the headbox), such as an air inflated rubber tube 69, positionedbetween the fixed end covers 67 and 68 and the end plates of adjustableroof portion 55, to prevent leakage of stock from the headbox.

Two positioning jacks 70 are mounted on brackets on columns 23, one oneach side of the machine, and are pivotally connected, through links 71,to apron member 38.

Thus headbox and reaction frame assembly 21 may be lifted by means oflifting jacks 26 to extract slice lips 47 and 48 from nip 72 betweenforming section rolls 73 and 74, for screen changes, maintenance,washup, etc. Lifting jacks 26 may also be used, in conjunction withpositioning jacks 70, to change the angle at which stock is ejectedthrough slice lips 47 and 48 into nip 72.

It will be appreciated that flexible plate type hinge 56 will not havesuflicient strength to constrain the internal stock pressures and tofully support adjustable roof portion 55. Thus to relieve hinge 56 ofany load carrying requirements, and to provide a positive means foradjustably positioning roof portion 55, a linkage mechanism 75 ispositioned on each side of the headbox. Particular reference now toFIGS. 6 to 12 shows in detail and in schematic arrangement, linkagemechanism 75 which provides a positive connection between adjustableroof portion 55 and the remainder of the headbox, and permits adjustableroof member 55 to be pivoted about main pivot pins 76 to achieveadjustment of slice gap 46. Hinge pins 76 are positioned in axialalignment with the centre of hinge reduced portion 57. Each linkagemechanism 75 comprises main pivot pin 76 which is rigidly secured tofixed end cover (67 or 68), pivot pin 77 which is rigidly secured to theend plate of fixed roof portion 54, pivit pin 78 which is rigidlyattached to brackets 79 on the outer surface of fixed roof portion 54,pivot pin 80 which is rigidly attached to the end plate of adjustableroof portion 55, and pivot pin 81 which is rigidly attached to brackets82 on the outer surface of adjustable roof portion 55.

Common screw member 83 is rotatably mounted in clevis 83a which ispivotally mounted on pivot pin 76 and contains two threaded portions 84and 85, the pitch of threaded portion 85 being twice that of threadedportion 84. Nut 86, having pivot pin 87 mounted thereon, is positionedon thread 84, and nut 88 having pivot pin 89 mounted thereon ispositioned on thread 85. Pivot pin 87 is operatively connected to pivotpins 77 and 80 by links 90 and 91, respectively. Pivot pin 89 isoperatively connected to pivot pins 78 and 81 by links 92 and 93,respectively. Pivot pins 76, 80 and 81, are also interconnected by link94.

Particular reference to FIGS. 10, 11 and 12 shows, schematically, theoperation of linkage mechanism 75.

In any given position, such as the position shown in full lines in FIG.10, the pivot pins assume a geometric arrangement in which the trianglesformed by pivot pins 76, 77 and 87; 76, 80 and 87; 76, 78 and 89; 76, 81and 89; are similar triangles. Thus when the fixed physical lengthbetween pivot pins 76 and 77 is arranged to be half of the fixedphysical length between pivot pins 76 and 78 and, similarly, when thefixed physical length between pivot pins 76 and 80 is arranged to behalf the flxed physical length between pivot pins 76 and 81, it will beseen that rotation of common screw 83 will cause nuts 86 and 88, andthus pivot pins 87 and 89, respectively, to move to positions 87a and89a, and the links will assume the geometric positions indicated by thebroken lines, with pivot pin 76 remaining as the common centre ofrotation for both geometric arrangements.

Reference to FIG. 11 shows a schematic arrangement of headbox 31 withlinkage 75 adjusted to provide a minimum slice gap 46. This correspondsto the full line geometric arrangement in FIG. 10. In FIG. 11 the gap95, between fixed roof portion 54 and adjustable roof portion 55, isshown as being parallel.

, Reference to FIG. 12 shows a schematic arrangement, similar to FIG.11, but in which linkage 75 has been adjusted, by rotation of commonscrew member 83, to provide a maximum slice gap 46a. This corresponds,though less exaggerated, with the broken line geometric arrangement inFIG. 10. In FIG. 12 the gap 95 is now shown to be substantially closedat the outer end and adjustable roof portion 55 is pivoted aboutflexible hinge 56 to provide the increased slice opening 46a.

It will thus be seen that rotation of common screw member 83 changes thegeometric arrangement of the links and, due to the fixed pivot points,causes adjustable roof portion 55 to pivot about pivot pin 76 and hinge56. It will also be seen that the link 94, interconnecting pivot pins76, and 81, prevents any loads being transferred to hinge 56.

It will be a simple mechanical expedient to provide for simultaneousoperation of common screw member 83, for maintenance of a parallel slicegap, etc., although each linkage 75 may be operated separately, ifrequired.

FIG. 13 shows a hydraulic circuit diagram of the apparatus for sensingthe pressure of the stock flowing through common passage 45 and forincreasing or decreasing the fluid pressure in cylinders 59 tocompensate for any changes in the stock pressure and thus to maintain abalanced state with the headbox structure in a condition of minimumdeflection.

Piezo-electric crystal 96 is mounted in adjustable roof portion 55 flushwith the surface of common stock passage 45. Piezo-electric crystal 96is sensitive to changes in pressure and will thus sense-changes in thepressure of the stock flowing through passage 45, which will producecorresponding changes in the capacitance of piezo-electric crystal 96.Piezo-electric crystal 96 is connected to an amplifier 97. An inputreference voltage is fed to amplifier 97 and the capacitance changes inpiezo-electric crystal 96 are amplified and reflected as changes in thevoltage fed to servo valve 98.

Servo valve 98 is positioned in the continually circulating hydraulicfluid circuit which provides the fluid pressure for hydraulic cylinders59. Pump 99, driven by motor 100, delivers hydraulic fluid from tank 101to pressure regulating valve 102. Pressure regulating valve 102 delivershydraulic fluid under pressure to hydraulic cylinders 59 and alsodirects the continuing flow of hyraulic fluid back to tank 101, viaservo valve 98 and pressure relief valve 103.

Thus, any changes in the capacitance of piezo-electric crystal 96 willbe reflected as a change in the voltage feed to servo valve 98, whichwill open or close the fluid restriction 104 and cause a decrease orincrease, respectively, in the pressure of the hydraulic fluid incylinders 59.

It will be understood that, although this specification illustratesquarter point positioning of the reaction and supporting members, whichrepresents the most economical manner for minimizing headboxdeflections, further supporting points can be provided to furtherminimize deflection, depending upon headbox design considerations suchas machine width, stock pressures, etc.

As an alternative execution of this invention the reaction frameassembly may be modified in shape to provide further space savings,provided its plane of maximum bending strength passes through theneutral axis of the apron member and it is pivotally connected theretoat least at the quarter point positions.

From the foregoing it is thus seen that a headbox according to theinvention accomplishes all of the objects and advantages as set forthherein.

What I claim is:

1. In a headbox for the discharge of stock onto a machine web formingsection, said headbox having stock inlet means, an adjustable orificeslice for discharging therethrough a web of varioble thickness and stockpassage means between said inlet means and said slice, the improvementcomprising reaction frame means surrounding said headbox having opposingelongated side members lying in a plane substantially normal to saidstock passage means, said headbox being operatively connected to saidreaction frame side members to minimize headbox deflection due to thepressure of stock flowing through said passage means.

2. The headbox as claimed in claim 1 having a hinged Wall portion ofsaid passage to permit adjustment of the slice, pivoted extensiblelinkage means connecting said hinged wall portion to fixed portions ofthe headbox, to provide mechanical adjustment of the slice, and loadbearing means connecting the opposing wall portion of the passage to theadjacent said frame side member in load transmitting relation therewith.

3. The headbox as claimed in claim 2 including at least one variableload transfer means connecting the movable wall portion of said passageto the adjacent one of said frame side members in load transfer relationtherewith.

4. The headbox as claimed in claim 3 including means for sensing thefluid stock pressure in said headboX, load controlling means connectedwith said load transfer means,

and means connecting said pressure sensing means with said loadcontrolling means, wherebythe transference of load from said movableWall portion to said frame side member is regulated in accordance withthe working pressure conditions in said headbox.

5. The headbox as claimed in claim 3 wherein said variable load transfermeans is connected to said movable Wall portion at substantially thequarter points along the length thereof, to provide minimal intermediatedeformation due to bending loads acting between said points ofconnection and to maintain the opening of said slice substantiallyparallel.

No references cited.

DONALL H. SYLVESTER, Primary Examiner.

A. C. HODGSON, Assistant Examiner.

1. IN A HEADBOX FOR THE DISCHARGE OF STOCK ONTO A MACHINE WEB FORMINGSECTION, SAID HEADBOX HAVING STOCK INLET MEANS, AN ADJUSTABLE ORIFICESLICE FOR DISCHARGING THERETHROUGH A WEB OF VARIOBLE THICKNESS AND STOCKPASSAGE MEANS BETWEEN SAID INLET MEANS AND SAID SLICE, THE IMPROVEMENTCOMPRISING REACTION FRAME MEANS SURROUNDING SAID HEADBOX HAVING OPPOSINGELONGATED SAID MEMBERS LYING IN A PLANE SUBSTANTIALLY NORMAL TO SAIDSTOCK PASSAGE MEANS, SAID HEADBOX BEING OPERATIVELY CONNECTED TO SAIDREACTION FRAME SIDE MEMBERS TO MINIMIZE HEADBOX DEFLECTION DUE TO THEPRESSURE OF STOCK FLOWING THROUGH SAID PASSAGE MEANS.